File 58da51e7-xenstored-Log-when-the-write-transaction-rate-limit.patch of Package xen.6121

References: bsc#1030144 XSA-206

Subject: xenstored: Log when the write transaction rate limit bites
From: Ian Jackson ian.jackson@eu.citrix.com Sat Mar 18 17:13:27 2017 +0000
Date: Wed Apr 5 15:26:29 2017 +0100:
Git: 3d00b3e8ac50671e8fe4a4c427686413a27324cb

Reported-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>

plus:

xenstore: dont increment bool variable
Instead of incrementing a bool variable just set it to true.

Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>

Index: xen-4.4.4-testing/tools/xenstore/xenstored_core.c
===================================================================
--- xen-4.4.4-testing.orig/tools/xenstore/xenstored_core.c
+++ xen-4.4.4-testing/tools/xenstore/xenstored_core.c
@@ -368,6 +368,7 @@ static void initialize_fds(int sock, int
 					POLLIN|POLLPRI);
 
 	wrl_gettime_now(&now);
+	wrl_log_periodic(now);
 
 	list_for_each_entry(conn, &connections, list) {
 		if (conn->domain) {
Index: xen-4.4.4-testing/tools/xenstore/xenstored_domain.c
===================================================================
--- xen-4.4.4-testing.orig/tools/xenstore/xenstored_domain.c
+++ xen-4.4.4-testing/tools/xenstore/xenstored_domain.c
@@ -24,6 +24,7 @@
 #include <stdarg.h>
 #include <xenctrl.h>
 #include <time.h>
+#include <syslog.h>
 
 #include "utils.h"
 #include "talloc.h"
@@ -80,6 +81,7 @@ struct domain
 	/* write rate limit */
 	wrl_creditt wrl_credit; /* [ -wrl_config_writecost, +_dburst ] */
 	struct wrl_timestampt wrl_timestamp;
+	bool wrl_delay_logged;
 };
 
 static LIST_HEAD(domains);
@@ -771,6 +773,7 @@ long wrl_ntransactions;
 
 static long wrl_ndomains;
 static wrl_creditt wrl_reserve; /* [-wrl_config_newdoms_dburst, +_gburst ] */
+static time_t wrl_log_last_warning; /* 0: no previous warning */
 
 void wrl_gettime_now(struct wrl_timestampt *now_wt)
 {
@@ -920,6 +923,9 @@ void wrl_check_timeout(struct domain *do
 	      wakeup);
 }
 
+#define WRL_LOG(now, ...) \
+	(syslog(LOG_WARNING, "write rate limit: " __VA_ARGS__))
+
 void wrl_apply_debit_actual(struct domain *domain)
 {
 	struct wrl_timestampt now;
@@ -935,6 +941,26 @@ void wrl_apply_debit_actual(struct domai
 	trace("wrl: domain %u credit=%ld (reserve=%ld)\n",
 	      domain->domid,
 	      (long)domain->wrl_credit, (long)wrl_reserve);
+
+	if (domain->wrl_credit < 0) {
+		if (!domain->wrl_delay_logged) {
+			domain->wrl_delay_logged = true;
+			WRL_LOG(now, "domain %ld is affected",
+				(long)domain->domid);
+		} else if (!wrl_log_last_warning) {
+			WRL_LOG(now, "rate limiting restarts");
+		}
+		wrl_log_last_warning = now.sec;
+	}
+}
+
+void wrl_log_periodic(struct wrl_timestampt now)
+{
+	if (wrl_log_last_warning &&
+	    (now.sec - wrl_log_last_warning) > WRL_LOGEVERY) {
+		WRL_LOG(now, "not in force recently");
+		wrl_log_last_warning = 0;
+	}
 }
 
 void wrl_apply_debit_direct(struct connection *conn)
Index: xen-4.4.4-testing/tools/xenstore/xenstored_domain.h
===================================================================
--- xen-4.4.4-testing.orig/tools/xenstore/xenstored_domain.h
+++ xen-4.4.4-testing/tools/xenstore/xenstored_domain.h
@@ -73,6 +73,7 @@ int domain_watch(struct connection *conn
 #define WRL_DBURST     10
 #define WRL_GBURST   1000
 #define WRL_NEWDOMS     5
+#define WRL_LOGEVERY  120 /* seconds */
 
 struct wrl_timestampt {
 	time_t sec;
@@ -88,6 +89,7 @@ void wrl_credit_update(struct domain *do
 void wrl_check_timeout(struct domain *domain,
                        struct wrl_timestampt now,
                        int *ptimeout);
+void wrl_log_periodic(struct wrl_timestampt now);
 void wrl_apply_debit_direct(struct connection *conn);
 void wrl_apply_debit_trans_commit(struct connection *conn);